Tropical Storm SURIGAE Advisory Çar, 21.04.

MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TYPHOON 02W (SURIGAE) WARNING NR 030//
RMKS//
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.
   TYPHOON 02W (SURIGAE), LOCATED APPROXIMATELY 297 NM
EAST-NORTHEAST OF MANILA, PHILIPPINES, HAS TRACKED NORTHWESTWARD
AT 07 KTS OVER THE PAST SIX HOURS. SURIGAE CONTINUES TO EXHIBIT A
LARGE 65 NM EYE, WHICH HAS WARMED IN RECENT HOURS. A REMNANT INNER
RING OF 40 NM DIAMETER CONTINUES TO CIRCULATE ALONG THE INNER RIM OF
THE PRIMARY EYEWALL. THE CORE REMAINS LARGELY SYMMETRIC, AS VERTICAL
WIND SHEAR (VWS) CONTINUES TO STAY UNDER 10 KTS. SATELLITE-BASED
INTENSITY ESTIMATES HAVE ASSUMED A WIDE RANGE OF VALUES OVER THE
PAST 12 HOURS, RANGING FROM AS HIGH AS 130-135 KTS FROM EARLIER
200930Z SMAP AND SAR PASSES, TO LOWER VALUES OF 116 KT FROM SATCON
AND 110 KT FROM ADT. BASED ON A COMBINATION OF THESE ESTIMATES,
ALONG WITH A 201800Z 6.0 (115 KTS) CURRENT INTENSITY ESTIMATE FROM
PGTW, THE INITIAL INTENSITY IS HELD AT 120 KTS. THE TYPHOON'S
OVERALL SATELLITE PRESENTATION HAS CHANGED LITTLE DURING THE PAST 24
HOURS, SAVE FOR CONTINUING DISSOLUTION OF THE INNERMOST CONVECTIVE
RING.
3. FORECAST REASONING.
   A. THERE IS NO SIGNIFICANT CHANGE TO THE FORECAST PHILOSOPHY
SINCE THE PREVIOUS PROGNOSTIC REASONING MESSAGE.
   B.  THROUGH 24 HOURS, SURIGAE WILL CONTINUE TRACKING NORTH-
NORTHWESTWARD TO THE EAST OF LUZON ALONG THE WESTERN PERIPHERY OF AN
UPPER-LEVEL RIDGE TO THE EAST. SURIGAE'S FORWARD SPEED HAS
INCREASED TO A SLIGHTLY BRISKER 07 KTS, WHICH IS LIKELY FAST ENOUGH
TO PREVENT OCEAN COOLING BENEATH THE TYPHOON FROM CAUSING WEAKENING,
BUT SLOW ENOUGH THAT INTENSIFICATION IS NOT EXPECTED. THE
LARGE AND STABLE CORE SIZE ALSO FAVORS LITTLE INTENSITY CHANGE UNTIL
THE ATMOSPHERIC ENVIRONMENT BECOMES MORE HOSTILE. THIS IS EXPECTED
TO OCCUR BEGINNING AROUND 36 HOURS AS A SHORTWAVE TROUGH WITHIN THE
SUBTROPICAL JET (STJ) APPROACHES FROM SOUTHEASTERN CHINA,
DRAMATICALLY INCREASING VWS TO AROUND 30 KTS. STEADY WEAKENING IS
EXPECTED TO ENSUE AFTER 36 HOURS AS THE TYPHOON ACCELERATES
NORTHEASTWARD AND THEN EASTWARD INTO THE MID-LATITUDE WESTERLIES. BY
AROUND 72 HOURS, THE AFOREMENTIONED SHORTWAVE IS EXPECTED TO
INTERACT DIRECTLY WITH SURIGAE. MODEL SOLUTIONS DIVERGE AT THIS
POINT. THE GFS POSITIONS SURIGAE DIRECTLY BENEATH THE BASE OF THE
SHORTWAVE, INDUCING RAPID WEAKENING AS THE TROUGH AXIS OUTRUNS THE
TYPHOON. OTHER MODELS SUCH AS THE JAPANESE GSM AND CANADIAN GEM
POSITION SURIGAE FARTHER AHEAD OF THE SHORTWAVE, ALLOWING INTENSITY
TO REMAIN HIGHER FOR LONGER. THE CURRENT FORECAST SPLITS BETWEEN
THESE OUTCOMES, SHOWING WEAKENING BELOW TYPHOON FORCE AFTER 72
HOURS. THE TRACK FORECAST IS SIMILAR TO THE PREVIOUS ONE, WITH HIGH
CONFIDENCE THROUGH 48 HOURS AND MODERATE CONFIDENCE THROUGH 72 HOURS.
   C. AFTER 72 HOURS, SURIGAE WILL INTERACT WITH A LOW-LEVEL THERMAL
GRADIENT SOUTH OF JAPAN, AS WELL AS THE AFOREMENTIONED UPPER-LEVEL
SHORTWAVE TO ITS NORTHWEST. WHILE MODELS DEPICT A RANGE OF POSSIBLE
ARRANGEMENTS OF THESE FEATURES, THE INCREASINGLY BAROCLINIC
ENVIRONMENT AROUND THE CYCLONE IS EXPECTED TO INDUCE THE ONSET OF
EXTRATROPICAL TRANSITION (ET). THE FORECAST IS HIGHLY DEPENDENT ON
THE DETAILS OF ET, AND THUS BOTH MODEL TRACK AND INTENSITY SPREAD IS
HIGH AFTER 72 HOURS. THE CURRENT FORECAST TRACK HAS BEEN NUDGED
SOUTHWARD AT 96 AND 120 HOURS TOWARD THE MULTI-MODEL CONSENSUS,
WHICH HAS SHIFTED SOUTHWARD DURING THE PAST 24 HOURS. WEAKENING TO
45 KTS IS FORECAST BY 120 HOURS WITHIN A HIGH SHEAR ENVIRONMENT, BUT
THIS FORECAST HAS BELOW-AVERAGE CONFIDENCE DUE TO THE AFOREMENTIONED
RANGE OF ET EVOLUTIONS.//
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